In a wireless communication node, such as a wireless repeater designed to operate with a wireless system capable of simultaneous transmission and reception of packets (i.e., duplex operation), the orientation of the antenna units can be important in establishing non-interfering operation as it is critical that the receiver is not desensitized by the transmitted signals. This can include networks that use time division duplex (TDD), frequency division duplex (FDD), or other desired methods of duplex operation.
Furthermore, enclosing antenna modules and repeater circuitry within the same package is desirable for convenience, manufacturing cost reduction and the like, but such packaging can give rise to interference problems.
In a full duplex repeater package, one antenna or set of antennae may operate with, for example, a base station, and another antenna may operate with a subscriber. Since the multiple signals of the same or different frequency will be transmitted and received in antennae that are close together, isolation of those antennae becomes important, particularly when simultaneous transmission and reception on both sides of the repeater are performed.
Furthermore, since the repeater unit houses all of the circuitry within a single package, it is desirable to closely position the antennae with minimal antenna-to-antenna interaction while maintaining acceptable gain and in many cases acceptable directivity.
For ease of manufacture, an exemplary repeater should be configured such that it can be easily produced in high volume manufacturing operations using low cost packaging. The exemplary repeater should be simple to set up to facilitate easy customer operation. Additional problems arise however when packaging repeater antennae and circuitry in close proximity. First, it becomes difficult to achieve high isolation between antennae due solely to the close physical proximity even where directional antennae are used.
Simply put, as the antennae are placed closer together, the more likely the antennae will couple energy into each other, which reduces the isolation between the sides of the repeater. Maintaining an omni or semi-omni directional antenna pattern becomes difficult since overlapping radiation patterns of antennae which are placed close to each other tend to generate interference effects. Energy from the antennae can further be electrically coupled through circuit elements such as through a shared ground plane especially in configurations where multiple antennas are integrated and the ground plane is small. While the use of direction antenna can benefit the repeater in terms of increased range and reduced wireless signal variation due to Raleigh fading effects, directional antennas are not typically used for indoor applications, due to the requirement for directional alignment, which is beyond the capability or desire of the average user.
Some improvements can be obtained through cancellation or similar techniques where a version of a signal transmitted on one side of the repeater is used to remove the same signal if it appears on the other side of the repeater. Such cancellation however can be expensive in that additional circuitry is required, and can be computationally expensive in that such cancellation can result in the introduction of a delay factor in the repeater or alternatively can require the use of more expensive and faster processors to perform the cancellation function.